City Council Speaker Christine Quinn has jumped to a 20-pointed lead over her nearest rival in the 2013 Democratic primary for mayor thanks largely to a surge of support from voters in her home borough of Manhattan, a new poll shows.

Pollster Lee Miringoff said Quinn’s soaring numbers in Manhattan — where she received 50 percent of the vote — were largely responsible for her new-found dominance in the crowded race. Since September, Quinn has doubled her level of support in the borough.

“Nobody else had a big group like that,” observed Miringoff.

Quinn’s strong showing was especially bad news for Stringer, who needs to emerge with big numbers in Manhattan to have any chance of winning City Hall. The poll indicated he was at a mere 10 percent.

Most analysts are predicting that the Democratic primary will end up in a runoff between the top two finishers, required by law if no candidate gets at least 40 percent.

Quinn allies are already talking her up as a lock for one of those spots.

“It’s very hard to see here not getting first or second (in the primary),” said one ally.

Quinn has enjoyed a burst of publicity recently over such high-profile issues as gay marriage to legislation she’s endorsed mandating a controversial “living wage” for employees of businesses receiving city subsidies.

Veteran political consultant Bruce Gyory cautioned that publicity early on doesn’t always translate into votes down the road.

“This could be cotton candy publicity,” he said. “Publicity is good. But does it provide nutrition?”

Gyory pointed out that at least three frontrunners for open mayoral seats had faded in the stretch since 1965.